Analgesics and Anti-inflammatory Drugs — MCQs

Analgesics and Anti-inflammatory Drugs Indian Medical PG Practice Questions and MCQs

Question 221: Which of the following statements about COX-2 is FALSE?

A. COX-2 is constitutively expressed on some cell surfaces.
B. Activation of COX-2 leads to an ulceroprotective effect on the gastric mucosa. (Correct Answer)
C. COX-2 is induced at the site of inflammation.
D. COX-2 is utilized in the generation of eicosanoids with a ring structure.

Explanation: **Explanation:** The core concept tested here is the physiological difference between the two isoforms of Cyclooxygenase (COX). **Why Option B is False (Correct Answer):** The **ulceroprotective effect** on the gastric mucosa is primarily mediated by **COX-1**, not COX-2. COX-1 is a "housekeeping" enzyme that produces Prostaglandin $E_2$ ($PGE_2$) and Prostacyclin ($PGI_2$) in the stomach, which inhibit acid secretion and stimulate mucus/bicarbonate production. In contrast, COX-2 is primarily associated with inflammation. While COX-2 does play a minor role in healing existing ulcers, it is not the primary mediator of gastric protection. **Analysis of Incorrect Options:** * **Option A:** While COX-2 is primarily inducible, it is **constitutively expressed** in specific tissues, most notably the **kidneys, brain, and vascular endothelium**. This is a high-yield fact often tested to explain the renal side effects of selective COX-2 inhibitors. * **Option C:** COX-2 is the **inducible** isoform. Its expression increases significantly (up to 20-fold) at sites of inflammation in response to cytokines (IL-1, TNF-$\alpha$) and growth factors. * **Option D:** Both COX-1 and COX-2 act on arachidonic acid to produce **prostanoids** (prostaglandins, prostacyclin, and thromboxane), all of which contain a characteristic **20-carbon fatty acid ring structure** (cyclopentane ring). **High-Yield Clinical Pearls for NEET-PG:** * **Selective COX-2 Inhibitors (Coxibs):** These drugs (e.g., Celecoxib, Etoricoxib) spare the gastric mucosa but increase the risk of **thrombotic cardiovascular events** because they inhibit endothelial $PGI_2$ (vasodilator/anti-aggregatory) without affecting platelet $TXA_2$ (vasoconstrictor/pro-aggregatory). * **Aspirin:** It is the only NSAID that causes **irreversible inhibition** of COX enzymes via acetylation. * **Glucocorticoids:** One of their primary anti-inflammatory mechanisms is the **inhibition of COX-2 gene expression**.

Question 222: Etanercept used in rheumatoid arthritis acts by?

A. Inhibition of COX2 and COX-3
B. Inhibition of TNFa (Correct Answer)
C. Potent immunosuppressive action
D. Auto-immunologically mediated action

Explanation: **Explanation:** **Mechanism of Action (Why B is correct):** Etanercept is a biological Disease-Modifying Antirheumatic Drug (bDMARD). It is a **soluble decoy receptor** produced by recombinant DNA technology. It consists of two molecules of the ligand-binding portion of the human **p75 TNF receptor** fused to the Fc portion of human IgG1. It works by binding to both **TNF-α and TNF-β**, preventing them from interacting with cell surface receptors, thereby neutralizing the pro-inflammatory cascade central to Rheumatoid Arthritis (RA). **Analysis of Incorrect Options:** * **Option A:** Inhibition of COX-2 is the mechanism of NSAIDs (e.g., Celecoxib), while COX-3 inhibition is associated with Paracetamol (Acetaminophen) in the CNS. Etanercept does not affect the arachidonic acid pathway. * **Option C:** While Etanercept is an immunomodulator, "potent immunosuppressive action" is a generic term more characteristic of drugs like Cyclosporine, Tacrolimus, or high-dose Corticosteroids which have broader effects on T-cell signaling. * **Option D:** This is a distractor term. While RA is an autoimmune disease, the drug’s specific pharmacological action is targeted cytokine neutralization, not a vague "auto-immunological" action. **High-Yield NEET-PG Pearls:** * **Mnemonic:** **Etanercept** "**Intercepts**" TNF (it is a receptor, not a monoclonal antibody). * **Suffix Clue:** Drugs ending in **-cept** are receptor fusion proteins; drugs ending in **-mab** (Infliximab, Adalimumab) are monoclonal antibodies. * **Pre-requisite:** Always screen for **Latent Tuberculosis** (via Mantoux or IGRA) before starting TNF inhibitors, as they can cause reactivation. * **Other Indications:** Psoriatic arthritis, Ankylosing spondylitis, and Plaque psoriasis.

Question 223: Ibuprofen acts by inhibiting which enzyme?

A. Lipooxygenase
B. Cyclooxygenase (Correct Answer)
C. Resetting the hypothalamic thermostat
D. Increasing the pain threshold

Explanation: **Explanation:** **Mechanism of Action (Why B is correct):** Ibuprofen is a prototypical **Non-Steroidal Anti-Inflammatory Drug (NSAID)** belonging to the propionic acid derivative class. Its primary mechanism of action is the **reversible, non-selective inhibition of the enzyme Cyclooxygenase (COX-1 and COX-2)**. By inhibiting COX, ibuprofen prevents the conversion of arachidonic acid into prostaglandins (PGs), specifically PGE2 and PGI2. These prostaglandins are key mediators of inflammation, pain sensitization, and fever induction. **Analysis of Incorrect Options:** * **A. Lipooxygenase (LOX):** This enzyme converts arachidonic acid into leukotrienes. While drugs like Zileuton inhibit LOX, standard NSAIDs like Ibuprofen do not; in fact, inhibiting COX can sometimes "shunt" arachidonic acid toward the LOX pathway, potentially worsening asthma (aspirin-exacerbated respiratory disease). * **C & D. Resetting the thermostat/Increasing pain threshold:** These describe the **physiological effects** (antipyretic and analgesic actions) resulting from PG inhibition, but they are not the biochemical mechanism or the enzyme being inhibited. **High-Yield Clinical Pearls for NEET-PG:** * **Pharmacokinetics:** Ibuprofen has a short half-life (~2 hours), requiring frequent dosing. * **Clinical Use:** It is the drug of choice for closing a **Patent Ductus Arteriosus (PDA)** in neonates (though Indomethacin is also used). * **Adverse Effects:** Compared to Aspirin, Ibuprofen causes less gastric irritation but can still cause interstitial nephritis and fluid retention. * **Contraindication:** Avoid in patients with the "Aspirin Triad" (Asthma, Nasal polyps, and NSAID sensitivity).

Question 224: Chemically, aspirin is:

A. Acetyl salicylic acid (Correct Answer)
B. Para-aminosalicylic acid
C. Para-aminobenzoic acid
D. Acetaminophen

Explanation: **Explanation:** **Aspirin** is the prototype of non-steroidal anti-inflammatory drugs (NSAIDs). Chemically, it is **Acetylsalicylic acid**, formed by the acetylation of salicylic acid. This chemical structure is crucial to its mechanism: aspirin irreversibly inhibits the **COX-1 and COX-2 enzymes** by transferring its acetyl group to a serine residue at the active site. This distinguishes it from other NSAIDs, which are reversible inhibitors. **Analysis of Incorrect Options:** * **B. Para-aminosalicylic acid (PAS):** This is a bacteriostatic antitubercular drug used in the treatment of multi-drug resistant tuberculosis (MDR-TB), not an analgesic. * **C. Para-aminobenzoic acid (PABA):** This is a precursor in bacterial folic acid synthesis. Sulfonamides act as structural analogs of PABA to inhibit bacterial growth. * **D. Acetaminophen:** Also known as Paracetamol, this is chemically **N-acetyl-para-aminophenol**. While it is an analgesic and antipyretic, it lacks significant peripheral anti-inflammatory activity. **High-Yield Clinical Pearls for NEET-PG:** 1. **Zero-Order Kinetics:** At high/toxic doses, aspirin metabolism shifts from first-order to zero-order kinetics. 2. **Antiplatelet Action:** At low doses (75–150 mg), it selectively inhibits Thromboxane A2 (TXA2), providing cardioprotection. 3. **Reye’s Syndrome:** Aspirin is contraindicated in children with viral infections (influenza/varicella) due to the risk of hepatic encephalopathy and fatty liver. 4. **Aspirin Triad (Samter’s Triad):** Consists of asthma, nasal polyposis, and aspirin intolerance. 5. **Toxicity:** Salicylism presents with tinnitus (earliest sign), respiratory alkalosis, and metabolic acidosis.

Question 225: Buprenorphine is classified as?

A. Partial agonist at mu receptor (Correct Answer)
B. Partial agonist at kappa receptor
C. Full agonist at mu receptor
D. Full agonist at kappa receptor

Explanation: **Explanation:** **Buprenorphine** is a semi-synthetic highly lipophilic opioid. It is classified as a **Partial Agonist at the mu (μ) receptor** and a **competitive antagonist at the kappa (κ) receptor**. 1. **Why Option A is correct:** As a partial mu-agonist, buprenorphine has a high affinity for the receptor but low intrinsic activity. This results in a "ceiling effect" for respiratory depression, making it safer in overdose compared to full agonists. However, it also exhibits a ceiling effect for analgesia. Its high affinity means it binds tightly and dissociates slowly, leading to a long duration of action. 2. **Why Options B & D are incorrect:** Buprenorphine acts as an **antagonist** (not an agonist) at kappa receptors. This property is clinically significant as it contributes to its antidepressant effects and reduces the risk of dysphoria and psychotomimetic effects typically associated with kappa stimulation. 3. **Why Option C is incorrect:** Full mu-agonists (like Morphine, Fentanyl, or Methadone) have high intrinsic activity and no ceiling effect for analgesia or respiratory depression. **High-Yield Clinical Pearls for NEET-PG:** * **Opioid Withdrawal:** Because of its high affinity, if buprenorphine is given to a patient physically dependent on full agonists (like heroin), it can displace the full agonist and precipitate **withdrawal symptoms**. * **Naloxone Resistance:** Due to its slow dissociation from mu receptors, buprenorphine-induced respiratory depression is difficult to reverse with standard doses of Naloxone. * **Clinical Uses:** Used in opioid detoxification (as a substitute for methadone) and for chronic pain management (Transdermal patches). * **Buprenorphine + Naloxone:** This combination is used sublingually to prevent intravenous abuse (Naloxone is not absorbed orally but triggers withdrawal if injected).

Question 226: Which of the following medications can cause hyperkalemia?

A. Amphotericin B
B. Beta agonists
C. Gentamicin
D. Succinylcholine (Correct Answer)

Explanation: **Explanation:** **Succinylcholine** is a depolarizing neuromuscular blocker that acts as an agonist at the nicotinic acetylcholine receptors (nAChR) of the motor endplate. Upon binding, it causes prolonged depolarization, leading to an efflux of intracellular **potassium (K+)** into the extracellular space. In healthy individuals, this typically results in a minor rise in serum potassium (0.5 mEq/L). However, in patients with "upregulation" of extrajunctional receptors (e.g., burns, massive trauma, or prolonged immobilization), this efflux can be massive and life-threatening. **Analysis of Incorrect Options:** * **Amphotericin B:** This antifungal is notorious for causing **hypokalemia** and hypomagnesemia due to its toxic effects on the distal renal tubules (Type 1 RTA), leading to increased potassium excretion. * **Beta agonists (e.g., Salbutamol):** These drugs stimulate the Na+/K+-ATPase pump, shifting potassium from the extracellular fluid into the cells. Consequently, they cause **hypokalemia** and are actually used in the emergency management of hyperkalemia. * **Gentamicin:** As an aminoglycoside, it can cause nephrotoxicity and electrolyte disturbances, most commonly **hypokalemia** and hypomagnesemia (Bartter-like syndrome). **NEET-PG High-Yield Pearls:** * **Succinylcholine Contraindications:** Avoid in patients with major burns (>24 hours old), crush injuries, spinal cord injuries, and muscular dystrophies (risk of rhabdomyolysis). * **Drug-Induced Hyperkalemia Mnemonic (K-BANK):** **K**-sparing diuretics, **B**eta-blockers, **A**CE inhibitors/ARBs, **N**SAIDs, and **K** (Potassium) supplements/Succinylcholine. * **Antidote:** There is no direct pharmacological reversal agent for Succinylcholine; it is metabolized by plasma pseudocholinesterase.

Question 227: Which of the following drugs inhibits Thromboxane A2 synthase?

A. Aspirin
B. Prednisolone
C. Dazoxiben (Correct Answer)
D. Naproxen

Explanation: **Explanation:** The correct answer is **Dazoxiben**. **1. Why Dazoxiben is correct:** Dazoxiben is a selective **Thromboxane A2 (TXA2) synthase inhibitor**. In the arachidonic acid cascade, the enzyme TXA2 synthase converts Prostaglandin H2 (PGH2) into Thromboxane A2 (a potent vasoconstrictor and platelet aggregator). By inhibiting this specific enzyme, Dazoxiben reduces TXA2 levels without significantly affecting the production of other prostaglandins or prostacyclin (PGI2). This makes it pharmacologically distinct from non-selective COX inhibitors. **2. Why the other options are incorrect:** * **Aspirin:** It is an irreversible inhibitor of **Cyclooxygenase (COX-1 and COX-2)**. While it ultimately reduces TXA2 production by blocking the upstream synthesis of PGH2, it does not inhibit the TXA2 synthase enzyme itself. * **Prednisolone:** This is a glucocorticoid that acts much higher in the inflammatory cascade. It induces lipocortin (annexin A1), which inhibits **Phospholipase A2**, thereby preventing the release of arachidonic acid from cell membranes. * **Naproxen:** Like Aspirin, this is a non-selective **COX inhibitor** (reversible). It blocks the conversion of arachidonic acid to PGH2. **3. NEET-PG High-Yield Pearls:** * **Selective TXA2 Synthase Inhibitors:** Dazoxiben and Ridogrel (Ridogrel also has TXA2 receptor-blocking properties). * **Aspirin "Anti-platelet" Dose:** Low doses (75–150 mg) selectively inhibit COX-1 in platelets, leading to a permanent deficit in TXA2 for the life of the platelet (7–10 days). * **Prostacyclin (PGI2):** Produced by vascular endothelium; it is the physiological antagonist of TXA2 (causes vasodilation and inhibits aggregation). Selective TXA2 synthase inhibitors are theoretically superior to Aspirin because they spare PGI2 production.

Question 228: The Mu receptor of opioids is responsible for which of the following clinical actions?

A. Analgesia
B. Respiratory depression
C. Sedation
D. Diuresis (Correct Answer)

Explanation: This question focuses on the specific physiological effects mediated by opioid receptor subtypes. While Mu ($\mu$) receptors are the primary targets for clinical analgesia, they are associated with **urinary retention**, not diuresis. ### **Why "Diuresis" is the Correct Choice (The Exception)** In the context of this question, **Diuresis** is the correct answer because it is **NOT** an action of the Mu receptor. Mu receptors (specifically $\mu_2$) stimulate the release of Antidiuretic Hormone (ADH) and increase sphincter tone, leading to urinary retention. * **Clinical Concept:** Diuresis is uniquely associated with the **Kappa ($\kappa$) receptor**. Kappa agonists inhibit the release of ADH (vasopressin) at the posterior pituitary, leading to increased free water clearance. ### **Analysis of Incorrect Options (Mu Receptor Actions)** * **A. Analgesia:** This is the hallmark effect of Mu receptors ($\mu_1$ for supraspinal and $\mu_2$ for spinal analgesia). * **B. Respiratory Depression:** This is the most dangerous side effect of Mu receptor activation ($\mu_2$), caused by decreased sensitivity of the brainstem to $CO_2$. * **C. Sedation:** Mu and Kappa receptors both contribute to drowsiness and sedation, though Mu-mediated sedation is more profound. ### **High-Yield Clinical Pearls for NEET-PG** * **Mu ($\mu$) Receptor Effects:** Analgesia, Respiratory depression, Miosis (Pin-point pupil), Reduced GI motility (Constipation), Euphoria, and Physical dependence. * **Kappa ($\kappa$) Receptor Effects:** Spinal analgesia, **Diuresis**, Dysphoria, and Psychotomimetic effects (hallucinations). * **Delta ($\delta$) Receptor Effects:** Spinal/Supraspinal analgesia and modulation of Mu receptor activity. * **Mnemonic:** Remember **"K"** for **K**appa and **"K"** for **K**idneys (Diuresis). Most other classic opioid side effects (The "3 Cs": Constipation, Coma/Resp Depression, Convulsions) are Mu-mediated.

Question 229: Febuxostat is indicated in the treatment of which condition?

A. Hyperkalemia
B. Hyperuricemia (Correct Answer)
C. Hypernatremia
D. Hypercalcemia

Explanation: **Explanation:** **Febuxostat** is a potent, non-purine selective inhibitor of **Xanthine Oxidase (XO)**. Xanthine oxidase is the key enzyme responsible for converting hypoxanthine to xanthine, and xanthine to uric acid. By inhibiting this enzyme, Febuxostat effectively lowers serum uric acid levels, making it a primary treatment for **Hyperuricemia** and chronic gout. **Why the other options are incorrect:** * **Hyperkalemia (High Potassium):** Managed with calcium gluconate (membrane stabilization), insulin-glucose infusion, or potassium binders (e.g., Patiromer). * **Hypernatremia (High Sodium):** Managed primarily with free water replacement or hypotonic fluids (e.g., 5% Dextrose). * **Hypercalcemia (High Calcium):** Managed with aggressive hydration, loop diuretics (Furosemide), bisphosphonates, or Calcitonin. **High-Yield Clinical Pearls for NEET-PG:** 1. **Mechanism of Action:** Unlike Allopurinol (a purine analog), Febuxostat is a **non-purine** inhibitor. It is more potent and does not require dosage adjustment in patients with mild-to-moderate renal impairment. 2. **Hypersensitivity:** It is a preferred alternative for patients who develop **Allopurinol Hypersensitivity Syndrome** or those with the HLA-B*5801 allele. 3. **Adverse Effects:** While generally well-tolerated, it carries a "Black Box Warning" for increased risk of **cardiovascular death** in patients with pre-existing heart disease. 4. **Drug Interactions:** Like Allopurinol, it should not be co-administered with **Azathioprine** or **6-Mercaptopurine**, as it can lead to life-threatening bone marrow toxicity due to decreased metabolism of these drugs.

Question 230: Which of the following has a high oral to parenteral activity ratio?

A. Morphine
B. Diacetyl morphine
C. Oxymorphine
D. Methadone (Correct Answer)

Explanation: ### Explanation The **oral to parenteral (O:P) activity ratio** refers to the effectiveness of a drug when administered orally compared to its effectiveness when given by injection. A high ratio indicates high oral bioavailability and minimal first-pass metabolism. **1. Why Methadone is Correct:** Methadone is a synthetic opioid with **excellent oral bioavailability (approx. 80-90%)**. Because it undergoes minimal first-pass hepatic metabolism, its oral potency is nearly equal to its parenteral potency. This high O:P ratio, combined with its long half-life, makes it the gold standard for **opioid substitution therapy** and chronic pain management, as it provides stable plasma levels without the need for frequent injections. **2. Analysis of Incorrect Options:** * **Morphine:** It has a **low O:P ratio (approx. 1:3 to 1:6)**. It undergoes extensive significant first-pass metabolism in the liver (glucuronidation), meaning an oral dose must be much higher than an IV dose to achieve the same analgesic effect. * **Diacetylmorphine (Heroin):** This is a highly lipophilic prodrug. While it is more potent than morphine when injected (crossing the blood-brain barrier rapidly), it is deacetylated to morphine in the gut and liver when taken orally, leading to significant loss of potency. * **Oxymorphone:** Similar to morphine, it has low oral bioavailability (approx. 10%) due to extensive first-pass metabolism, necessitating much higher oral doses compared to parenteral administration. **3. NEET-PG High-Yield Pearls:** * **High O:P Ratio Drugs:** Methadone, Levorphanol, Codeine, and Oxycodone. * **Low O:P Ratio Drugs:** Morphine, Hydromorphone, and Oxymorphone. * **Methadone Mechanism:** It is a $\mu$-opioid receptor agonist, an **NMDA receptor antagonist**, and a monoamine reuptake inhibitor. * **Clinical Note:** Methadone is known for causing **QT interval prolongation**; baseline ECG is recommended before starting therapy.

Practice by Chapter

NSAIDs: Classification and Mechanism

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COX-2 Selective Inhibitors

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Acetaminophen (Paracetamol)

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Opioid Analgesics and Antagonists

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Drugs Used in Gout and Hyperuricemia

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Drugs Used in Rheumatoid Arthritis

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Disease-Modifying Antirheumatic Drugs

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Glucocorticoids as Anti-inflammatory Agents

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Migraine Therapeutics

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Neuropathic Pain Management

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